The present invention relates generally to radio frequency identification (RFID) test systems and devices. More particularly, the present disclosure relates to an RFID test system that establishes a minimum coupling between two ports without an RFID tag present and a higher coupling when the RFID tag is present.
Radio frequency identification (RFID) devices are well known and are increasingly utilized in a wide variety of applications. However, one challenge associated with RFID devices (e.g., RFID tags, RFID labels, RFID chips, RFID straps, or RFID inlays) is the manufacture and testing of the RFID devices in a high-volume and cost-effective manner.
For example, during or after the manufacturing process, the RFID devices may be tested while located in close proximity to each other (e.g., adjacent RFID devices closely spaced). The RFID devices, as an example, may be manufactured on a common carrier web, with the RFID device (e.g., an RFID inlay) having its antenna mounted on the common carrier web and its integrated circuit mounted to the antenna.
Due to the close proximity of the RFID devices, it may be difficult to establish bi-directional communication with each of the RFID devices during testing. In general, an antenna of the RFID device may be viewed as having a near field region and a far field region. The near field region refers to a reactive near field and a radiating near field, while the far field region refers to a radiating far-field component. Short-range testing of RFID devices generally involves testing within the near field region (e.g., utilizing the near or far-field components), while long-range testing generally involves testing within the far field region.
For short-range testing and long-range testing, typically certain precautions must be taken, when testing one of the RFID devices, to prevent the RFID devices that are in close proximity from also responding or affecting the test results for each RFID device being tested. This results in complicated test procedures or test setups and may lead to operational RFID devices that are tested and erroneously determined to be defective. As a result, there is a need for improved test techniques for RFID devices.
The present invention discloses an RFID test system that establishes a minimum coupling between two ports without an RFID tag present and a higher coupling when the RFID tag is present. Furthermore, this controlled coupling in the presence of an RFID tag is used to read and identify tags. The RFID tag is read when it is in the coupling zone, as it receives maximum power and has the lowest loss path to the receiver. Adjacent tags do not couple efficiently, so they are isolated from the wanted device (i.e., RFID tag). Further, the coupling through the RFID tag can be frequency specific, and the peak frequency can be determined. This peak frequency and also the amount of coupling can give a good indication of a number of aspects of the tag assembly.